The effect of late season drought stress on some morphophysiological characteristics of Iranian safflower varieties in Karaj region

In order to investigate the effects of late-season drought stress on some morpho-physiological characteristics of Iranian safflower varieties, an experiment was conducted in the research field of Karaj Seed and Plant Improvement Research Institute. This study included two irrigation levels; normal irrigation (control) and drought stress from grain filling stage (main plot), and five Iranian safflower varieties including Sofeh, Goldasht, Golmehr, Padideh and Parnian (sub-plot), which conducted as a split-plot experiment in a randomized complete block design with three replications during the 2016- 17. The results showed that drought stress had a significant effect on morpho-physiological traits and yield of safflower varieties and decreased plant height, heads per plant, head diameter, seeds per head, 1000-seed weight and grain yield. Moreover, drought stress reduced relative water content, leaf area index and increased canopy temperature of safflower varieties. Drought stress reduced seed yield and oil content of safflower seeds by 14.9 and 2.7%, respectively. The echo-physiological response of safflower varieties to drought stress was different. Due to the number of heads and 1000-seed weight Parnian variety had the highest grain yield at both control and stress conditions by 2150 and 1773 kg/ha, respectively. The highest grain yield loss due to drought stress was observed in Sofeh variety by 24.8%. Parnian variety had the highest relative water content and leaf area index and the lowest canopy temperature under drought stress. So, Parnian was a drought-tolerant variety.